Body Tissues

The human body, complex as it is, starts out a single cell, the fertilized egg,
which divides almost endlessly. The millions of cells that result become
specialized for particular functions.
Tissues – group of cells that are similar in structure and function.

The four primary tissue types:

1. Epithelial (covering)
2. Connective Tissue (support)
3. Muscle (movement)
4. Nervous (control)
Histology: microscopic study of tissues
› Biopsy: removal of tissues for diagnostic purposes
› Autopsy: examination of organs of a dead body
to determine cause of death
 1. Epithelial Tissue
Epithelium is the lining, covering and glandular tissue of the body.
Covering and lining epithelium covers all free body surfaces both
inside and out, and contains versatile cells.
•
Epithelial functions include:
Protection
Absorption
Filtration
Secretion
Hallmarks of Epithelium:
 Specialized cell contacts bind
adjacent cells together
 Polarity has apical, basal, and
lateral surfaces
 Rests on a basement membrane
 Avascular has no blood supply of
their own
 Regenerate easily
 Classification of Epithelia
› Number of layers of cells
– Simple- one layer of cells; each extends from
basement membrane to the free surface
– Stratified- more than one layer.
– Pseudostratified- tissue appears to be stratified, but
all cells contact basement membrane so it is in fact
simple
› Shape of cells
– Squamous- flat, scale-like
– Cuboidal- about equal in height and width
– Columnar- taller than wide
Simple Epithelia › more concerned with absorption,
secretion, and filtration.
› because they are very thin, protection is
not one of their specialties.
Stratified Epithelia › two or more cell layers
› more durable than simple epithelia;
function primarily in protection
 Stratified Cuboidal & Columnar
Epithelia
2. Stratified cuboidal epithelium
has two or mare cell layers with the surfaces are being
cuboidal in shape.

3. Stratified columnar epithelium

columnar cells, but its basal cell vary in size and shape.

› Both epithelia are fairly rare in the body,

found mainly in the ducts of large glands.
 Glandular Epithelium
A gland consists of one or more cells that make and secrete a
particular product.
Secretion – contains protein molecules in an aqueous fluid.

Two types of glands develop from epithelial sheets:

1. Endocrine glands: they are often called ductless glands;
their secretion (all hormones) diffuses directly into the blood
vessels. (e.g., thyroid, adrenals, pituitary and etc.)
2. Exocrine glands: open to exterior of body via ducts
(e.g., sweat glands, oil glands, liver, and pancreas)
2. ConnectiveTissue
Connects body parts; found everywhere in the body. It is
most abundant and wide distributed of the tissue types.
•
Connective tissue functions:
Protection
Support
Binding
Hallmarks of Connective Tissue:
 Variation in blood supply most connective
tissue are well vascularized, but there are
exceptions.
 Connective tissue are made up of may
different type of cells
 Extracellular matrix- nonliving substance
found outside the cells
 Connective Tissue Cells
 Fibroblasts - secrete the proteins needed for fiber synthesis and
components of the extracellular matrix
 Adipose or fat cells (adipocytes). common in some tissues
(dermis of skin)
 Mast cells. common beneath membranes; along small blood
vessels; release heparin, histamine, and proteolytic enzymes in
response to injury.
 Leukocytes (WBC’s). respond to injury or infection
 Macrophages. derived from monocytes (a WBC).
Phagocytic; provide protection
 Chondroblasts - form cartilage
 Osteoblasts - form bone
 Hematopoietic stem cells - form blood cells
 Undifferentiated mesenchyme (stem cells). have potential to
differentiate into adult cell types.
 Extracellular Matrix
The matrix is produced by the connective tissue
cells and then secreted to their exterior.

It has two main elements:

1.Ground substance –structureless material
that fills the space between cells
2.Fibers – collagen, elastic, or reticular
 Ground Substance
› Interstitial (tissue) fluid within which are one or
more of the molecules listed below:
• Hyaluronic acid: a polysaccharide. Very slippery;
serves as a good lubricant for joints. Common in
most connective tissues.
• Proteoglycans: protein and polysaccharide
complex. Polysaccharides called
glyocosaminoglycans (chondroitin sulfate, keratin
sulfate). Protein part attaches to hyaluronic acid. Able
to trap large amounts of water.
• Adhesive molecules: hold proteoglycan aggregates
together. Chondronectin in cartilage, osteonectin in
bone, fibronectin in fibrous connective tissue.
› Functions as a molecular sieve through which nutrients
diffuse between blood capillaries and cells
 Protein fibers
› Collagen fibers. Composed of the protein
collagen. Strong, flexible, inelastic; great
tensile strength (i.e. resist stretch). Perfect
for tendons, ligaments

› Elastic fibers. Contain molecules of protein

elastin that resemble coiled springs.
Returns to its original shape after stretching or
compression. Perfect for lungs, large blood
vessels

› Reticular fibers. Formed from fine

collagenous fibers; form branching networks
(stroma). Fill spaces between tissues and
organs.
 Major Connective Tissue
1. Bone
2. Cartilage
3. Dense Connective Tissue
4. Loose Connective Tissue
5. Blood
Bone
Cartilage › less hard & more flexible than bone
› its major cell type is chondrocytes
› only few in the body
Dense Connective Tissue
Loose Connective Tissue
Blood › Vascular tissue consists of blood cells &
blood plasma
3. Muscle Tissue
› Characteristics
 Cells are referred to as fibers
 Contracts or shortens with force when
stimulated
 Moves entire body and pumps blood
› Types
1. Skeletal: attached to bones
2. Cardiac: muscle of the heart
3. Smooth: nonstriated and involuntary
4. Nervous › Functional characteristics are
irritability & conductivity
Tissue